#!/usr/bin/env python

#输出1-1/2+1/3-1/4+1/5.......+1/99-1/100的结果（保留两位小数）

i=1
amount=0
while i<=100 :
    if i%2==0:
        amount-=1/i
    else:
        amount+=1/i
    i+=1
amount=round(amount,2)
print(amount)
